I'd say there's a high probability it's going to be Boom Boom Rocket. xbox360achievements announced the achievement list for it a few days back with a sly "expect to see this very soon" comment.
I know that Boom Boom have said that it is going to be released mid April, which obviously leaves this week or next week, and I found out about sensi from a web-page, will try and find it again................
However I do sense you may be right Tetlee, because by now the title for the week has normally been specified. Could be a no-show.